Hello folks. I'm looking to do a motion control videography related project. One motor will carry a platform on a track, the other will spin a turn table. The turn table won't require a lot of speed, but will be carrying about 8-9lbs. The platform on the track will be carrying less weight, but may need to move the platform at about 2 feet per second. Both will ramp up to full speed, stop at a particular spot, and return to their starting position when done to repeat the same motions again and again exactly. The turn table will be directly bolted to one motor. The platform/track will move with a timing pulley on a belt.
From what I've gathered in my research I need stepper motors, most likely Nema 23. I've been looking at hybrid motors with more torque. What I'm wondering is this:
• Should I pick bipolar or unipolar motors. I've read the differences and am still unsure. One seems easier to program than the other, but I may be incorrect.
• What motor controllers should I pick? Do I need one controller per motor if they are on a single Arduino (I need simultaneous startup)?
• What Arduino model would be best? I don't mind wired control of everything.
Help with these three questions is greatly appreciated.
Mark2000:
The turn table will be directly bolted to one motor. The platform/track will move with a timing pulley on a belt.
No, I'd strongly suggest use a reduction belt drive for the turntable too, or else a geared stepper, that sounds like a
large amount of moment of inertia on that turntable, far more than a bare motor could hope to control.
You also need to worry about angular resolution and steppiness if you did direct drive.
From what I've gathered in my research I need stepper motors, most likely Nema 23. I've been looking at hybrid motors with more torque. What I'm wondering is this:
• Should I pick bipolar or unipolar motors. I've read the differences and am still unsure. One seems easier to program than the other, but I may be incorrect.
Low/mid impedance bipolar, no doubt whatsoever, you'll need microstepping to avoid horrible vibration.
2 to 5 ohms sort of range is about right
• What motor controllers should I pick? Do I need one controller per motor if they are on a single Arduino (I need simultaneous startup)?
A microstepping driver than can handle the current of your motor. If you go for a very low impedance
motor that will force an expensive industrial driver since only they can handle currents above about 2A.
Somewhat higher impedance allows less expensive single-chip drivers (but limits the top speed somewhat)
• What Arduino model would be best? I don't mind wired control of everything.
shouldn't matter, you don't have many output pins to control
Help with these three questions is greatly appreciated.
You should be think about figuring out the accelerations and angular accelerations involved, that
will determine the torque needed from the motors and allow selection of the right size motors.
BTW the turntable will need a thrust-bearing / lazy-susan to take all the weight - the motor should not use abused for
this purpose, you'll risk trashings its bearings.
I assume the TB6560 handles a hybrid since it has 6 pins. Is one type of motor easier to program than the other?
MarkT:
BTW the turntable will need a thrust-bearing / lazy-susan to take all the weight - the motor should not use abused for
this purpose, you'll risk trashings its bearings.
I was planning to use a lazy susan bearing. Will that make direct drive make sense, or do you still recommend a belt driven turntable? In the record player world direct is more precise than belt, but, obviously, this is a different situation.
You know, I feel a little bad, because all these ebay links will break and then...
Ok, that link is to a six-wire motor. That motor will work fine.
As a matter of fact, you have a bit of flexibility because you can use it in full-coil or half-coil configuration.
half-coil = less low-speed torque but more torque at the higher end.
full-coil = 4x the inductance, so less torque at high speed. But more holding torque and slow-speed torque.
MarkT:
A Nema17 might be enough for the turntable if sensibly geared, we need those acceleration figures to
work that out....
The turntable will probably not need to go faster than one full revolution per minute. As I said, it will be carrying 8lbs while it's doing it.
The dolly will be pulled by a closed loop timing belt with a 80 tooth gt2 pulley on either end. The dolly will have to move at a max speed of 2 feet per second, which, if my math is correct, is 240 rpm. It should be carrying 4-5 lbs total - though I'd want some leeway here to go heavier.
